(Table 1) Stable oxygen and carbon isotope composition of bivalve shells of sediment core CRP-1, and of Wright Valley and McMurdo Sound

Shells from a middle Pleistocene carbonate-rich unit (lithostratigraphic Unit 3.1; 33.82-3 1.89 metres below sea floor) have d180 values between +3.64 and +4.56 per mil PDB and d13C between +0.85 and + 1.09 per mil PDB.

Oxygen isotopic compositions are close to or at equilibrium conditions with scawater at a temperature in the range of c. -2 to 0°C in the absence of melt water influx. Thus, the CRP-1 carbonate-unit was deposited under 'interglacial' polar conditions, comparable to those of the present-day and isotope stage 3 in the Ross Sea. 'Chlamys' sp. 1, retrieved from a lower Miocene diamictite at 62.19 mbsf, is the only unaltered shell of this age in CRP-1 and yielded a d18O value of -4.64 per mil PDB and d13C of -3.35 per mil PDB.